1. Fields of the Invention
The present invention relates generally to an access control system or a security system, and particularly to an improvement on a recognition apparatus and method for security systems.
2. Description of the Prior Art
The use of pin codes in conjunction with user input identification codes has always been implemented as a means of increasing the security of an access control system in the access control industry. A user identification number is a number (typically stored on a magnetic card) which is given to a user and the user identification number has an associated pin code number. When a person wants to gain access to an access control system, he or she enters (typically by a keyboard) the pin code number and its associated user identification number (hereinafter referred to as "user number") into the system to let the recognition apparatus check the user identification number based on the user number.
For an access control system sold to different purchasers, such as different hotels or offices, if the pin codes for the same available user numbers at different hotels or offices are the same, the security of each of the hotels or offices equipped with such a system may be compromised because the users assigned with the same user number at different hotels or offices may gain access into more than one hotel or office by also using the same pin code number. Therefore, it is desirable that different pin codes be used for available user numbers at different locations of purchasers of the access control system. It is also desirable that the pin codes used for available user numbers be quickly and easily modified by the purchasers or manufacturer without changing of any circuitry or software of the access control system. Accordingly, various scrambling methods for differentiating the pin codes at different locations have been developed for enhancing the security of access control systems used by many customers. A possible choice of a pin code number associated with a user number under a scrambling principle or method is a so-called scramble mode . For an access control system, the more "scramble modes" that are available, the more security is achieved. If there are thousands of scramble modes available for an access control system, such a system is not easily accessed by a person without a correct pin code number even if the scrambling method has been reverse engineered.
The pin code recognition technique normally utilizes a programmed microprocessor or logic circuits as pin code recognition equipment for determining the authenticity of a user number and an associated pin code number entered by a person for access to an access control system. The access control system may be a security lock system, a bank cashing system, a membership checking system, a community facility or the like. Whenever access is desired, a user number and a pin code number are generally entered into a recognition apparatus; then, the recognition apparatus processes the user number in a predetermined manner and derives therefrom data which is compared with the pin code input so that the authenticity of the pin code input is determined. If the pin code is authentic, then the user is granted access to the facility.
A typical prior art computer system for authenticating a pin code includes the steps of choosing one or more sets of data bits (variables) of a user number input, generating a matrix index value by using the variables in predetermined equations, using the obtained matrix index to obtain a constant from a predetermined matrix, and then, comparing the constant value with the corresponding digit of the pin code input. If the two values match each other, then the remaining other digits of the pin code input are checked in a similar manner. Suppose the user number is a four-digit decimal number, this number occupies 16 bits in a binary computer. A number of variables, such as A-F (as shown below) can be obtained by defining several octal numbers, each of which contains three binary bits, as shown in the following table 1:
TABLE 1 ______________________________________ B Octal Variable B B F B B B Bits Occupied by B B B B B B B B B B B B B B B B B B Binary User No. BxBxBxBxBxBxBxBxBxBxBxBxBxBxBxBxB B Octal Variable B A B B B C B D B E B B ______________________________________
The predetermined equations for generating the matrix indice can be algebraic equations. Different equations having different combinations of the defined variables will result in different octal digit values. Such digit values will be used as matrix indices in a row of an 8 by 8 matrix stored in a ROM to determine a constant for comparison with the pin code input. Since the matrix is an 8 by 8, diagonally, symmetric matrix, there are eight scramble modes available to such method or recognition apparatus. In other words, if there is a pin code book for such a security system, only eight sets of pin code numbers or eight scramble modes can be selected for the system. When more than eight customers use this system, some customers have to use the same scramble mode. Further, the system is easily accessed if someone familiar with this art knows the scrambling method because the system has very limited number of scramble modes.
One of the important problems with such conventional methods is that the number of scramble modes available is very limited so that the security of access control systems using such techniques is very much reduced.